Spaun J, Lyng J
Bull World Health Organ. 1970;42(4):523-34.
Since 1935 the International Unit for Tetanus Antitoxin has been defined as the activity contained in a certain weight of the first International Standard for Tetanus Antitoxin. As stocks of this standard had become depleted, 11 laboratories in 8 countries were requested to participate in a collaborative assay of a preparation proposed as a replacement.The assay results were analysed and presented to the WHO Expert Committee on Biological Standardization in 1969 which established the preparation studied as the second International Standard for Tetanus Antitoxin and defined the International Unit for Tetanus Antitoxin as the activity contained in 0.03384 mg of the second International Standard for Tetanus Antitoxin. This definition would ensure the continuity of the size of this international unit.The analysis of the collaborative studies also showed that the second International Standard for Tetanus Antitoxin has suitable properties for use in the flocculation test for the determination of the antigen content of tetanus toxoids in Lf values. The designation Lf-equivalent is described and the problems relating to the use of this term for the expression of results of in vitro assays are analysed in relation to the use of international units for expressing results of in vivo assays. As the second International Standard for Tetanus Antitoxin has an in vivo/in vitro ratio of 1.4, the Lf-equivalent of this antitoxin is 1.4 times less than its unitage.
自1935年以来，破伤风抗毒素国际单位被定义为一定重量的第一份破伤风抗毒素国际标准品中所含的活性。由于该标准品的库存已消耗殆尽，于是邀请了8个国家的11个实验室参与对一种拟作为替代品的制剂进行协作测定。1969年对测定结果进行了分析，并提交给世界卫生组织生物标准化专家委员会，该委员会将所研究的制剂确立为破伤风抗毒素第二国际标准品，并将破伤风抗毒素国际单位定义为0.03384毫克破伤风抗毒素第二国际标准品中所含的活性。这一定义将确保该国际单位大小的连续性。协作研究分析还表明，破伤风抗毒素第二国际标准品具有适用于以絮状试验测定破伤风类毒素Lf值中抗原含量的特性。描述了“Lf当量”这一名称，并分析了在体外试验结果表达中使用该术语与在体内试验结果表达中使用国际单位相关的问题。由于破伤风抗毒素第二国际标准品的体内/体外比值为1.4，该抗毒素的Lf当量比其单位效价少1.4倍。
